1. Field of the Invention
The invention relates generally to downhole equipment for use in wells, and more particularly to modular gauges that are configured to be used with electric submersible pump (“ESP”) systems that employ “wet connections” to supply power to the pump motors.
2. Related Art
A pump may be required to produce fluid from a well. Electric submersible pumps “ESP's” are typically used for this purpose. Conventionally, an ESP is connected to the end of tubing that is then lowered into the well. The tubing is positioned so that the ESP is located in the well bore where fluid from the surrounding geological formation is allowed to flow into the well. Gauges can be attached at the bottom of the ESP system to allow various parameters (e.g., motor temperature, fluid temperature, fluid pressure, etc.) to be monitored and communicated to the surface, either through dedicated communication lines, or via “comms-on” transmissions over the power cable.
Conventionally, power is provided to the ESP through a cable that transmits power (typically three-phase power) from a motor controller at the surface of the well to the ESP system. The power cable is attached to a connector at the top of the ESP's motor and runs from the motor, along the outside of the tubing, to the motor controller. If gauges are used, electrical connections are made between the gauge and motor before the gauge unit is attached to the bottom of the motor. This enables communications between the gauges and surface equipment through the motor via the power cable.
If there are problems with the pump, motor or gauges, they must be removed from the well so that they can be repaired or replaced. In a conventional installation, because the ESP is secured to the bottom of the tubing string, the tubing and cable must be pulled out of the well in order to reach the pump, motor and/or gauges. Removing the tubing normally requires the use of a work over or drilling rig, which is expensive and impacts well production based on rig availability and work over time.
The expense of removing the tubing, cable and attached equipment from wells using conventional rigs has led to the development of retrievable ESP systems that employ “wet connections” to couple the pump and motor to the power source on the surface. In these systems, a portion of the electrical connection is secured near the lower end of tubing/production conduit which has a large enough diameter to install the ESP system inside it. The power cable is attached to the outside of the tubing as in a conventional system, but the power cable ends at a connector near the end of the tubing. After the tubing (with the power cable) is installed in the well, the pump and motor can be connected to wireline, wire rope, coiled tubing or jointed pipe which then allows the ESP system to be conveyed/lowered into the well inside the larger-diameter tubing/production conduit. When the pump and motor reach the bottom of the production conduit, a series of conductors at the bottom of the pump motor engages the conductors in the electrical connection near the bottom of the production conduit. This completes the connection between the power cable and the ESP pump motor so that the pump can be operated to produce fluid from the well.